AMF Security Context Transfer via Integrity-Protected Registration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the handover scenario from a 4G to a 5G communications system, the first AMF faces challenges in obtaining the security context of user equipment from the second AMF, as existing methods do not adequately ensure the integrity of the transfer process.
Innovation Solution
The first AMF integrity-protects a registration request message using a native security context with the second AMF, allowing the second AMF to validate its integrity, thereby ensuring successful transfer of the security context.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first AMF sends a registration request message to the second AMF without integrity protection, then the message transfer is simple and fast, but the integrity of the message cannot be ensured, leading to validation failure
Solution Approach 1:
The first AMF performs integrity protection on the registration request message in advance before sending it to the second AMF. This preliminary security processing ensures that the message integrity is maintained during transfer, and the second AMF can successfully validate the message without requiring complex additional verification mechanisms.
2Reliability
If the first AMF uses a mapped security context for integrity protection, then the security context is available, but the second AMF cannot validate the message because it lacks the corresponding security context
Solution Approach 1:
The first AMF acts as an intermediary that translates the security context from the mapped security context (based on 4G parameters) to a format compatible with the second AMF's native security context (based on 5G parameters). This translation enables the second AMF to validate the integrity-protected message successfully, bridging the gap between different security context domains.
3Reliability
If the system requires strict integrity validation of the registration request message, then security is improved, but the message transfer may fail due to integrity protection mismatches
Solution Approach 1:
The first AMF changes the parameters of the integrity protection by adapting the mapped security context (derived from 4G parameters like K_ASME and NH) to match the parameter structure expected by the second AMF's native security context (based on 5G parameters like K_AMF and NG_KSI). This parameter adaptation ensures that strict integrity validation can be performed without causing validation failures, thereby maintaining both security assurance and handover efficiency.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Embodiments of this application provide a security context obtaining method. After user equipment UE is handed over from a 4G communications system to a 5G communications system, a first AMF providing an access and mobility management service for the UE in the 5G system may obtain a security context of the UE from a second AMF in the 5G communications system according to the method. The method includes: The UE sends a first registration request message to the first AMF, where the first registration request message carries a second registration request message. The first AMF sends the second registration request message to the second AMF, where the second registration request message is integrity protected using a native security context between the UE and the second AMF. After successfully validating integrity of the second registration request message, the second AMF returns the security context of the UE to the first AMF. This method can improve a possibility that the first AMF successfully obtains the security context of the UE from the second AMF.